For artillery ammunition with medium and large calibre, it is increasingly being sought to obtain entirely combustible propellant charges which make it possible to overcome the constraints linked with the use of non-combustible metal cases. Furthermore, since the propellant charge is to be alterable as a function of the parameters of the shot envisaged, a particularly advantageous solution is that proposed by modular charges.
Such charges consist of identical modules composed of a cylindrical combustible housing having a central channel and filled with a propellant powder charge. As a function of the parameters of the shot, the user of the weapon determines the number of modules to use and, possibly, their nature.
Although the solution of entirely combustible modular charges is of very great theoretical interest, it is in practice of limited use because of the complexity hitherto involved in the practical production of such modular charges.
A first embodiment was proposed by Patent Application FR-A-2,497,335. According to this application, the combustible housing comprises a body and a bottom, a cover and a central tube. These various elements are made from combustible elements in plate form by thermoforming and are bonded to one another. A first drawback presented by this solution resides in the correct positioning of the various elements constituting the housing and, in particular, in the correct positioning of the central tube intended for transmitting the ignition from one housing to another. A second drawback resides in the use of combustible materials which are to undergo a thermoforming operation.
In order to overcome this second drawback, the person skilled in the art then sought to use combustible housings obtained by a felting technique.
Another solution, described in U.S. Pat. No. 4,922,823, thus consists in making the housing by assembling and bonding to each other two hollow combustible cylindrical elements which are each closed at one of their ends by a plane face having a central orifice bordered by an internal neck with a height less than the height of the said element. At the moment of assembling the two elements, it is necessary to fit the central tube which consists of agglomerated propellant powder and which bears on the two central necks. A first drawback of such a solution is the practical difficulty of carrying out such an assembly. A second drawback is the difficulty of completely filling such a housing with the loose propellant powder.
A solution, which is similar to the former, was proposed by Patent Application EP-A-0,475,207.
This solution also consists in producing the combustible housing from two hollow combustible cylindrical elements which are each closed at one of their ends by a plane face having a central orifice and are assembled and bonded to one another. The central channel is a hollow tube of agglomerated propellant powder bearing on the inside of the two plane faces and the propellant charge is a hollow cylindrical block of agglomerated propellant powder. This solution has the drawback of being limited to propellant charges of agglomerated powder and, moreover, has the additional problem of correct positioning of the central tube.
Solutions currently known to Applicants Company therefore all have the major drawback of resorting to a modular charge with constituent elements which do not incorporate the central tube intended to transmit the ignition, in order to constitute the cylindrical housing. These solutions therefore all require fitting the central tube during assembly of the housing, which fitting is difficult for batch production. In addition, the housings thus obtained are often difficult to completely charge with the loose powder. Finally, it should be noted that the more separate parts a housing contains, the greater is its cost price.